CN113203893B - Inductor and method for extracting alternating current resistance of coil winding of loosely coupled transformer - Google Patents
Inductor and method for extracting alternating current resistance of coil winding of loosely coupled transformer Download PDFInfo
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- 238000005859 coupling reaction Methods 0.000 claims abstract description 32
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Abstract
The invention relates to a method for extracting alternating current resistance of a coil winding of an inductor and a loose coupling transformer, which comprises the following steps: step S1, obtaining the winding voltage and the winding inductance of the magnetic coupling system to be measured and measuring the alternating current resistance of the magnetic coupling system; step S2, calculating the winding current according to the obtained winding voltage, winding inductance and the measured alternating current resistance of the magnetic coupling system; step S3, obtaining the magnetic core loss through finite element simulation software; and step S4, calculating the alternating current resistance of the winding according to the obtained core loss and the winding current. The invention separates the winding alternating current resistance loss from the magnetic core loss, thereby obtaining the equivalent resistance of the winding alternating current loss under different frequencies, solving the problems of low measurement efficiency and large calculated amount when the number of Litz wire strands is large in the prior art, and being suitable for measuring the winding alternating current resistance of an inductor, a loose coupling transformer with large leakage inductance or coupling inductance.
Description
Technical Field
The invention relates to the field of magnetic coupling system detection, in particular to a method for extracting winding alternating current resistance of an inductor and a loosely coupled transformer.
Background
Magnetic elements (including inductors and transformers) in a switching power supply system operate under high frequency current excitation conditions to achieve energy storage and transfer. The coil winding can generate serious high-frequency eddy current effect in high-frequency operation, so that the resistance of the coil can be greatly increased along with the change of frequency, and the direct current resistance of the coil can not be used for representing the resistance. In order to increase the inductance and the coupling coefficient of the transformer and to shield the electromagnetic field, a magnetic core is often added to the magnetic element. In general, for an inductor and a loosely coupled (small coupling coefficient) transformer having a magnetic core structure, the ac resistance of the magnetic element winding cannot be measured by a small-signal measuring instrument such as an LCR meter. This is because the measured resistance includes not only the ac resistance of the winding but also the high-frequency loss resistance of the magnetic core. Of course, if the conductor used for the winding of the magnetic element is an enameled wire or a copper foil, the ac resistance of the coil winding can be obtained by finite element simulation, but in engineering applications, Litz wire is often used as the conductor of the winding in order to reduce the winding loss. The number of Litz wire strands is large, and if finite element software is adopted for simulation, the calculation resources are extremely huge, calculation results are difficult to obtain, and the engineering practical value is not achieved.
Disclosure of Invention
In view of the above, an object of the present invention is to provide an inductor and a method for extracting ac resistance of a coil winding of a loosely coupled transformer, in which ac resistance loss of the coil winding is separated from magnetic core loss, so as to obtain equivalent resistance of ac loss of the winding at different frequencies, and solve the problems of low measurement efficiency and large calculation amount when there are many Litz wire strands in the prior art, and the method is suitable for measuring ac resistance of a winding of a loosely coupled transformer or a coupled inductor with large leakage inductance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for extracting the alternating current resistance of a coil winding of an inductor and a loosely coupled transformer comprises the following steps:
step S1, obtaining the winding voltage and the winding inductance of the magnetic coupling system to be measured and measuring the alternating current resistance of the magnetic coupling system;
step S2, calculating the winding current according to the obtained winding voltage, winding inductance and alternating current resistance of the measuring magnetic coupling system;
step S3, obtaining the magnetic core loss through finite element simulation software;
and step S4, calculating the alternating current resistance of the coil winding according to the obtained magnetic core loss and winding current.
Further, the step S1 is specifically: measuring winding inductance by impedance analyzerL measureAnd measured AC resistance of magnetic coupling systemR measure(ii) a Measuring amplitude of excitation voltage of winding by voltage probeU measure。
Further, the winding current amplitude specifically is as follows:
whereinZ measureIn order to measure the impedance of the device,L measurethe inductance measured for the frequency range from 1/5 to 1/10 at which the winding self-resonates.
Further, the step S3 is specifically:
step S31: establishing a three-dimensional simulation model of the magnetic coupling system to be tested in an eddy current field and setting corresponding material attributes;
step S32: the method comprises the following steps of equivalently replacing an actual coil winding by a round wire or a copper sheet of a closed loop, and setting corresponding material properties;
step S33, according to the measured exciting current, the total magnetic core loss P is obtained by giving the winding exciting current simulationcore。
Further, the coil winding AC resistanceR wExpressed as:
whereinR eqcoreEquivalent core loss resistance.
Compared with the prior art, the invention has the following beneficial effects:
the invention separates the winding alternating current resistance loss from the magnetic core loss, thereby obtaining the equivalent resistance of the winding alternating current loss under different frequencies, solving the problems of low measurement efficiency and large calculated amount when the number of Litz wire strands is large in the prior art, and being suitable for measuring the winding alternating current resistance of a loose coupling transformer or a coupling inductor with large leakage inductance.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a flow chart of core loss simulation according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a three-dimensional simulation model of a magnetic coupling structure including a magnetic core according to an embodiment of the present invention;
fig. 4 is a measurement equivalent circuit diagram after the secondary side of the magnetic coupling system is opened according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
Referring to fig. 1, the present invention provides a method for extracting ac resistance of a coil winding of an inductor and a loosely coupled transformer, comprising the following steps:
step S1, obtaining the winding voltage and the winding inductance of the magnetic coupling system to be measured and measuring the alternating current resistance of the magnetic coupling system;
step S2, calculating the winding current according to the obtained winding voltage, the winding inductance and the alternating current resistance of the measuring magnetic coupling system;
step S3, obtaining the magnetic core loss through finite element simulation software;
and step S4, calculating the alternating current resistance of the coil winding according to the obtained magnetic core loss and winding current.
Preferably, in this embodiment, the coil winding inductance is measured by an impedance analyzerL measureAnd measuring the AC resistance of the magnetic coupling systemR measure(ii) a Measuring amplitude of excitation voltage of winding by voltage probeU measure。
AC resistance of magnetic coupling system measured by impedance analyzerR measureExpressed as:
wherein, the first and the second end of the pipe are connected with each other,I Rpkm、I Rc、I measureare current amplitudes.
Applying sinusoidal current excitation to an impedance analyzerI measureLower core lossP coreAs is known, this can be expressed according to the equivalent circuit of fig. 4 as:
simultaneous winding flowPassing currentI measureCan be driven by an excitation voltageU measureAnd measuring impedanceZ measureExpressed as:
whereinZ measureIn order to measure the impedance of the device,L measurethe measured inductance is measured for the frequency range of 1/5 to 1/10 at the point where the winding self-resonates.
Further, the coil winding AC resistanceR wExpressed as:
whereinR eqcoreIs equivalent core loss resistance
In this embodiment, preferably, step S3 specifically includes:
step S31: establishing a three-dimensional simulation model of the magnetic coupling system to be tested in an eddy current field or a transient field and setting corresponding material attributes;
step S32: a round wire or a copper sheet of a closed loop is adopted to equivalently replace a coil winding, and corresponding material properties are set;
and step S33, simulating to obtain the total magnetic core loss by giving excitation current to the winding according to the measured excitation current.
Example 1:
for the magnetic coupling structure containing the magnetic core in the wireless power transmission system, as shown in fig. 3, the coupling coefficient is low, and the ac resistance of the winding cannot be obtained by using the conventional measurement and simulation method. The method proposed by the invention is now used to obtain the winding ac resistance.
As shown in Table 1, the excitation voltages at the two ends of the primary side at each subharmonic frequency point measured by an impedance analyzer after the secondary side of the magnetic coupling structure with the magnetic core is openedU measureAnd a measuring resistorR measure。
TABLE 1 Primary side terminal voltage and test resistance at each subharmonic frequency point
| Measured value | 40kHz | 120kHz | 200kHz | 280kHz | 360kHz |
| U measure/V | 1.245 | 1.455 | 1.475 | 1.495 | 1.515 |
| R measure/ WΩ | 0.088W | 0.226W | 0.570W | 1.179W | 2.328W |
Combined with measured primary inductanceL p=264.92mH and formula can determine the excitation current flowingI measureAs shown in table 2.
TABLE 2 Primary side excitation Current at each subharmonic frequency Point
| Calculated value | 40kHz | 120kHz | 200kHz | 280kHz | 360kHz |
| I measure/mA | 0.0189 | 0.0221 | 0.0224 | 0.0227 | 0.0230 |
As shown in Table 3, the secondary side of the magnetic coupling structure obtained by finite element simulation software has no exciting current, while the primary side applies exciting currentI measureObtaining the magnetic core loss at each harmonic frequency pointP core。
TABLE 3 magnetic core losses at various subharmonic frequency points for the primary side
| Simulation value | 40kHz | 120kHz | 200kHz | 280kHz | 360kHz |
| P core/mW | 0.90 | 6.05 | 12.71 | 20.88 | 30.46 |
Further according to a formula, the equivalent resistance of the magnetic core loss under each subharmonic frequency point can be calculatedR eqcoreAC resistance with primary windingR wAs shown in table 4.
TABLE 4 Primary winding AC resistance and core loss equivalent resistance of the primary at each subharmonic frequency
| Calculated value | 40kHz | 120kHz | 200kHz | 280kHz | 360kHz |
| R eqcore/ WΩ | 0.005 | 0.025 | 0.051 | 0.081 | 0.115 |
| R w/ WΩ | 0.083 | 0.201 | 0.519 | 1.098 | 2.213 |
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (4)
1. A method for extracting the alternating current resistance of a coil winding of an inductor and a loosely coupled transformer is characterized by comprising the following steps of:
step S1, obtaining the winding excitation voltage, the winding inductance and the alternating current resistance of the magnetic coupling system to be measured;
step S2, calculating the winding excitation current required by finite element simulation according to the obtained inductance of the winding and the winding excitation voltage amplitude;
step S3, obtaining the magnetic core loss through finite element simulation software;
step S4, calculating the alternating current resistance of the coil winding according to the obtained magnetic core loss and the winding excitation current;
alternating current resistance R of the coil windingwExpressed as:
wherein R iseqcoreIs equivalent core loss resistance, LmeasureIs a winding inductance, RmeasureAn alternating current resistor of the magnetic coupling system; u shapemeasureThe winding excitation voltage, ω, is the angular velocity.
2. The method of claim 1, wherein the step S1 is specifically as follows: measuring winding inductance L by impedance analyzer or LCR metermeasureAnd measuring the alternating current resistance R of the magnetic coupling systemmeasure(ii) a Measuring the winding excitation voltage U by means of a voltage probemeasure。
3. The method of claim 1, wherein the winding excitation current is selected from the group consisting of:
wherein ZmeasureFor measuring impedance, LmeasureThe inductance measured for the frequency range from 1/5 to 1/10 at which the winding self-resonates.
4. The method of claim 1, wherein the step S3 is specifically as follows:
step S31: establishing a three-dimensional simulation model of a magnetic core of the magnetic coupling system to be tested in an eddy current field or a transient field and setting corresponding material attributes;
step S32: a round wire or a copper sheet of a closed loop is adopted to equivalently replace a coil winding, and corresponding material properties are set;
step S33, according to the measured winding excitation current, obtaining the magnetic core loss P by giving the winding excitation current simulationcore。
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| US8054593B2 (en) * | 2008-12-29 | 2011-11-08 | Reid Paul A | Apparatus and method for measuring load current using a ground fault sensing transformer |
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| US8823370B2 (en) * | 2011-08-31 | 2014-09-02 | Virginia Tech Intellectual Properties, Inc. | High frequency loss measurement apparatus and methods for inductors and transformers |
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| CN103630746B (en) * | 2013-12-04 | 2016-03-09 | 福州大学 | A kind of measurement and assessment have the method for air gap magnetic cell winding AC resistance |
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| CN106291123B (en) * | 2016-08-05 | 2019-03-12 | 福建工程学院 | A kind of method directly measuring magnetic cell winding loss |
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